Gastroesophageal reflux occurs when stomach acid intermittently surges into the esophagus. It is common for most people to experience acid reflux activity occasionally as heartburn. Gastroesophageal reflux disease (GERD) is a clinical condition in which the reflux of stomach acid into the esophagus is frequent enough and severe enough to impact a patient's normal functioning or to cause damage to the esophagus.
In the lower part of the esophagus, where the esophagus meets the stomach, there is a muscular valve called the lower esophageal sphincter (LES). Normally, the LES relaxes to allow food to enter into the stomach from the esophagus. The LES then contracts to prevent stomach acids from entering the esophagus. In GERD, the LES relaxes too frequently or at inappropriate times allowing stomach acids to reflux into the esophagus.
The most common symptom of GERD is heartburn. Acid reflux also leads to esophageal inflammation, which causes symptoms such as painful swallowing and difficulty swallowing. Pulmonary symptoms such as coughing, wheezing, asthma, or inflammation of the vocal cords or throat may occur in some patients. More serious complications from GERD include esophageal ulcers and narrowing of the esophagus. The most serious complication from chronic GERD is a condition called Barrett's esophagus in which the epithelium of the esophagus is replaced with abnormal tissue. Barrett's esophagus is a risk factor for the development of cancer of the esophagus.
Accurate diagnosis of GERD is difficult but important. Accurate diagnosis allows identification of individuals at high risk for developing the complications associated with GERD. It is also important to be able to differentiate between gastroesophageal reflux, other gastrointestinal conditions, and various cardiac conditions. For example, the similarity between the symptoms of a heart attack and heartburn often lead to confusion about the cause of the symptoms.
One method of diagnosing GERD is to monitor the pH in the lower esophagus at or somewhat above the upper boundary of the lower esophageal sphincter.
Existing esophageal pH monitoring devices are often intubated nasally using a wired monitor. Such systems are often left in place for twenty-four hours or longer. Such systems are typically unpopular with patients who sometimes find the protrusion of a wire for such an extended period of time.
At least one other esophageal pH monitoring has been used which deposits a remote monitoring capsule in the esophagus of a patient using a catheter. The remote monitoring capsule transmits pH information from the esophagus to an external receiver and remains in place up to a day or longer before detaching from the esophagus and passing harmlessly through the digestive system.
In either of these esophageal pH monitoring systems, it is important to place the monitoring device in the proper location in the esophagus. Typically, the proper location is determined as a function of the lower esophageal sphincter. Since the most severe effects of GERD are found in the lower esophagus nearest the lower esophageal sphincter, it is important to be able to locate a location in the esophagus as a function of the lower esophageal sphincter.
Such a position can be located, for example, visually through the use of an endoscope. However, while some doctors are comfortable in the use of an endoscope, others, principally surgeons, typically rely on manometry to determine the proper location.
Conventionally, manometry is done trans-nasally since a trans-nasal intubation is typically considered less intrusive for the patient. Further, manometry is also typically done with water due to its compatibility with the patient and because it can provide accurate pressure measurements.
Manometry accomplished in this manner involves placing a catheter trans-nasally into the esophagus through the lower esophageal sphincter and into the stomach. Water at a pressure is applied through the lumen in the catheter and the distal end of the catheter is moved upwards through the lower esophageal sphincter. The pressure sensed from the applied water pressure will increase as the distal end of the catheter passes through the restricted area of the lower esophageal sphincter.